Cuba has released more than half of the 53 political prisoners it promised to free as part of a deal made with the U.S. in December, a Miami-based Cuban exile and human rights activist group confirmed Thursday evening.

Thus far, 28 dissidents have been released from prisons throughout the island, according to the Foundation for Human Rights in Cuba (FHRC). Among the freed prisoners are 16 members of UNPACU, the Patriotic Union of Cuba, considered to be the country's most vehemently anti-government dissident group, as well as members of the Ladies in White, the opposition group made up of the wives and female relatives of jailed political prisoners in Cuba.

Among those released were Haydee Gallardo S., a Lady in White, and her husband Angel Figueredo C. who were both arrested in May 2014 on charges of "public disorder." The independent rap artist Ángel Yunier Remón Arzuaga, known as "El Crítico," was also released Thursday. 'El Critico" was sentenced to eight years in prison without a trial in March 2013 for "resistance" against the communist regime.

The FHRC told Fox News Latino that some prisoners, particularly members of UNPACU, have been released under the condition that may never leave the island again.

Neither the Obama administration nor the Cuban government have spoken publicly about the releases, or given a full list of names of the prisoners released since both governments brokered a deal on December 17th in which Cuba agreed to reestablish diplomatic relations.

In addition to the 53 political prisoners, the U.S. secured the release of American contractor Alan Gross. For its part, the U.S. let go three Cuban citizens held as spies on American soil.

The FHRC, which sends humanitarian aid to the families of political prisoners in Cuba, said it has not received any details from the Obama Administration as to who is being released and when. The organization has had to rely on their own sources on the ground to confirm the identities of the freed prisoners.

The lack of transparency and the secrecy surrounding the identities of the political prisoners drew criticism from FHRC's leader, Francisco Hernandez, as well as from top U.S. conservatives like Sen. Marco Rubio, R-Fla, who is also a Cuban-American.

"We would like to know the names, because obviously these people are going to need help when they are released, and we want to make sure that they are released," Hernandez told Fox News Latino. "Everyone is mute, why is that?"

The FHRC is demanding the names of the 53 political prisoners to ensure that the Castro regime is held accountable if they renege on their promise.

"To tell you the truth, I don’t know, after all these years, how this government can be so naïve with the Castros," Hernandez said.

One of the concerns is that the Castro regime could release political prisoners and then exile them for life from the island, keeping the prisoners from ever seeing their families again. In the past, the regime has freed political prisoners only to exile them in an effort to stop them from promoting freedom on the island.

Hernandez also thinks the Castro regime could choose to instead release common criminals, instead of actual political prisoners, because they are afraid of re-energizing the opposition on the island.

An FHRC press release on Thursday reiterated that there is still work to be done.

"The FHRC continues to call on the Obama Administration and the Vatican to demand the immediate release of all remaining Human Rights activists, permanently and without conditions, including forced exile, parole, house arrest, and or any type of further harassment, detainment, or repression for political motives."